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Coho Salmon Range

The coho salmon is one of seven species of Pacific salmon belonging to the genus Oncorhynchus, and one of two native salmon species regularly occurring in California. It occurs naturally in the north Pacific Ocean and tributary drainages. It ranges in freshwater drainages from Hokkaido, Japan and eastern Russian, around the Bering Sea and Aleutian Islands to mainland Alaska, and south along the North American coast to Monterey Bay, California (Figure 1).

Coho salmon historically ranged from the Oregon/California border (including the Winchuck and Illinois river drainages) south to the streams of the northern Monterey Bay (Snyder 1931; Fry 1973) including small tributaries to San Francisco Bay (Brown and Moyle 1991, Leidy and Becker 2001) (Figure 2). However, there is some evidence that they historically ranged as far south as the Pajaro River (Anderson 1995), the Big Sur River (Hassler et al. 1991), or even the Santa Ynez River (Lucoff 1980, as cited in National Council on Gene Resources 1982), although evidence of spawning populations south of the Pajaro River is anecdotal (Anderson 1995). Currently, the southernmost stream that contains coho salmon is Aptos Creek in Santa Cruz County (NMFS 2001a). Present distribution is shown in Figure 3.

Information on coho salmon in the San Joaquin and Sacramento rivers is sparse. Fry (1973) states that coho salmon did not occur in the Sacramento/San Joaquin river system prior to attempts to introduce them beginning in 1956. Hatchery fish returned in large numbers and spawned naturally, but were unable to maintain a natural run. Moyle (1976) notes that coho salmon in the Sacramento River are rare. It is likely that coho salmon historically observed in these streams were occasional strays (Hallock and Fry 1967; Hopkirk 1973). Intensive sampling efforts (trawling and beach seining) by the United States Fish and Wildlife Service (USFWS) in the Sacramento and San Joaquin rivers and estuary have recorded no coho salmon caught since the project began in 1976 (USFWS 2001 unpublished data). For these reasons, the Department does not consider the Sacramento/San Joaquin river system to be within the historical range of coho salmon.

Figure 1. Native range of coho
salmon (after Sandercock 1991).

Figure 2. Historical distribution
of coho salmon in California

Figure 3. Present distribution of coho salmon in California. Shading depicts the general range of coho salmon. Coho salmon may not be present in all streams within the shaded area.